1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to an LCD capable of securing a wide viewing angle by forming a plurality of liquid crystal cells having different liquid crystal cell sizes and different cell gaps over one mother glass.
2. Description of the Related Art
Traditionally, a cathode ray tube (CRT) has been used as an information display device because of advantageous characteristics such as better image quality on a screen and lower price. However, due to the poor portability of the CRT because of its size and weight, liquid crystal display devices (LCDs) have been actively developed in recent years. The LCD devices meet the demand of lightweight and miniaturized size. Furthermore, the LCD devices include more powerful performances, for example, micronization and low power consumption or the like, to overcome the disadvantages of the CRT. Thus, the LCD devices gained popularly as the mainstream information processing apparatuses of today.
The LCD includes a thin film transistor (TFT) and a pixel electrode formed on a substrate (i.e., TFT substrate), and a color filter substrate where a red, a green, and a blue color filters are formed. The TFT acts as a switching device. The LCD further includes a liquid crystal film interposed between the TFT substrate and the color filter substrate, thereafter two substrates are attached to each other. A plurality of liquid crystal cells having the same cell region are formed over a mother glass. In addition, a multi mode on glass (MMG) model LCD has been developed, in which the liquid crystal cells having different sizes are formed on the single mother glass.
FIG. 1 is a schematic view illustrating a related art MMG model LCD. As shown in FIG. 1, liquid crystal cells having cell regions I and II with different sizes are formed on a mother glass 10. The two substrates, the TFT substrate and the color filter substrate, are attached to each other in these regions. A first cell region I includes a large-sized liquid crystal cell having a size of 20 inches or more, whereas a second cell II includes a smaller-sized liquid crystal cell having a size of 15 inches or less. Since the liquid crystal cells having the cell regions I and II are formed simultaneously over one mother glass 10 in the MMG model, the liquid crystal panels of various sizes may be manufactured through one process. In FIG. 1, each capital letter H in the liquid crystal cells denotes the cell gap and it is understood that all of the liquid crystal cells have the same cell gap H regardless of the cell size according to the related art MMG model LCD.
FIG. 2A is a schematic view illustrating a location where a column spacer is formed in a pixel region according to the related art MMG model LCD. FIG. 2B is a cross-sectional view taken along line III-III′ of FIG. 2A. As shown in FIG. 2A, a gate line 21 is arranged in a horizontal direction crossing a data line 23 to define the pixel region, and a pixel electrode 29 is arranged in the pixel region. In addition, a TFT (i.e., a switching device) is formed at an intersection of the gate line 21 and the data line 23.
A column spacer 25 is formed over the gate line 21 to maintain a predetermined cell gap, or alternatively positioned over the gate line 21 to maintain the predetermined cell gap when attaching the color filter substrate to the TFT substrate. The column spacer 25 may be formed by patterning, on the TFT substrate or the color filter substrate. The region where the column spacer 25 is formed or positioned over the gate line 21 is a blocking region.
As shown in FIG. 2B, the gate line 21, a gate insulating layer 12 and a passivation layer 9 are formed over a first insulating substrate 11b in sequence. A reference numeral 29 denotes a pixel electrode. Over the column spacer 25, a color filter substrate including a black matrix 4, a color filter layer 5 and a common electrode 6 is formed over a second insulating substrate 11a. The column spacer 25 is placed over the gate line 21 (i.e., the blocking region of the TFT substrate) and under the black matrix 4 (i.e., the blocking region of the color filter substrate) to maintain the cell gap between the two insulating substrates 11a and 11b. 
FIG. 3 is a cross-sectional view illustrating the cell gap of two liquid crystal cells in the related art MMG model LCD. Referring to FIG. 3, when the column spacer 25 is formed in a predetermined shape as illustrated in FIGS. 2A and 2B, the height of cell gap in the first cell region I and II are equal. Accordingly, when the liquid crystal cells having different sizes from one another are formed as in the related art MMG model, the liquid crystal panels with various sizes may be manufactured through single process.
However, as illustrated in FIG. 3, since the cell gaps of the all liquid crystal cells are identically formed regardless of resolution or size of each cell, it is difficult to manufacture the LCD having various viewing angles. For example, after cutting the liquid crystal cells from the related art MMG model mother glass, a wide view polarizer must be attached to secure a wide viewing angle. Thus, the wide view polarizer plays a major role in securing the wide viewing angle that corresponds to a retardation value And of the liquid crystal cell.
However, if all the liquid crystal cells having different resolution and sizes are formed such that they have the same cell gap regardless of the cell size or the like, all the retardation values become equal to one another. As a result, all the liquid crystal cells have the same viewing angle regardless of their size or the like. Therefore, various-sized liquid crystal cells cannot be formed using one glass substrate to secure an optimized viewing angle in each liquid crystal cell.